<template>
  <div class='music-list'>
    <div class='back'
         @click='back'>
      <i class='icon-back'></i>
    </div>
    <h1 class='title'
        v-html='title'></h1>
    <div class='bg-image'
         :style='bgStyle'
         ref='bgImage'>
      <div class='play-wrapper'>
        <div class='play'
             v-show='songs.length>0'
             ref='playBtn'
             @click='random'>
          <i class='icon-play'></i>
          <span class='text'>随机播放全部</span>
        </div>
      </div>
      <div class='filter'
           ref='filter'></div>
    </div>
    <div class='bg-layer'
         ref='layer'></div>
    <scroll @scroll='scroll'
            :probe-type='probeType'
            :listen-scroll='listenScroll'
            :data='songs'
            class='list'
            ref='list'>
      <div class='song-list-wrapper'>
        <song-list :rank='rank'
                   :songs='songs'
                   @select='selectItem'></song-list>
      </div>
      <div class='loading-container'
           v-show='!songs.length'>
        <loading></loading>
      </div>
    </scroll>
  </div>
</template>

<script type="text/javascript">
import Scroll from 'base/scroll/scroll'
import SongList from 'base/song-list/song-list'
import Loading from 'base/loading/loading'
import { prefixStyle } from 'common/js/dom'
import { mapActions } from 'vuex'
import { playlistMixin } from 'common/js/mixin'

const RESERVED_HEIGHT = 40
const transform = prefixStyle('transform')
const backdrop = prefixStyle('backdrop-filter')
export default {
  name: 'MusicList',
  mixins: [playlistMixin],
  props: {
    bgImage: {
      type: String,
      default: ''
    },
    songs: {
      type: Array,
      default: () => []
    },
    title: {
      type: String,
      default: ''
    },
    rank: {
      type: Boolean,
      default: false
    }
  },
  computed: {
    bgStyle () {
      return `background:url(${this.bgImage})`
    }
  },
  created () {
    this.probeType = 3
    this.listenScroll = true
  },
  mounted () {
    this.imageHeight = this.$refs.bgImage.clientHeight
    this.minTranslateY = -this.imageHeight + RESERVED_HEIGHT
    this.$refs.list.$el.style.top = `${this.imageHeight}px` // 设置歌单距离顶部高度
  },
  data () {
    return {
      scrollY: 0
    }
  },
  methods: {
    handlePlaylist (playlist) {
      const bottom = playlist.length > 0 ? '60px' : '' // miniplayer高度60px
      this.$refs.list.$el.style.bottom = bottom
      this.$refs.list.refresh()
    },
    selectItem (item, index) {
      this.selectPlay({ // 触发actions 使player显示
        list: this.songs,
        index
      })
    },
    random () {
      this.randomPlay({
        list: this.songs
      })
    },
    scroll (pos) {
      this.scrollY = pos.y
    },
    back () {
      this.$router.back()
    },
    ...mapActions([
      'selectPlay',
      'randomPlay'
    ])
  },
  watch: {
    scrollY (newY) {
      let translateY = Math.max(this.minTranslateY, newY)
      let zIndex = 0
      let scale = 1
      let blur = 0
      this.$refs.layer.style[transform] = `translate3d(0,${translateY}px,0)`
      const percent = Math.abs(newY / this.imageHeight)
      if (newY > 0) {
        scale = 1 + percent
        zIndex = 10
      } else {
        blur = Math.min(20 * percent, 20)
      }
      this.$refs.filter.style[backdrop] = `blur(${blur}px)`
      if (newY < this.minTranslateY) { // 上滑过程中防止文字遮住图片
        zIndex = 10
        this.$refs.bgImage.style.paddingTop = 0
        this.$refs.bgImage.style.height = `${RESERVED_HEIGHT}px`
        this.$refs.playBtn.style.display = 'none'
      } else {
        this.$refs.bgImage.style.paddingTop = '70%'
        this.$refs.bgImage.style.height = 0
        this.$refs.playBtn.style.display = ''
      }
      this.$refs.bgImage.style['z-index'] = zIndex
      this.$refs.bgImage.style[transform] = `scale(${scale})`
    }
  },
  components: {
    Scroll,
    SongList,
    Loading
  }
}
</script>

<style scoped lang="stylus" rel="stylesheet/stylus">
@import '~common/stylus/variable'
@import '~common/stylus/mixin'
.music-list
  position: fixed
  z-index: 100
  top: 0
  left: 0
  bottom: 0
  right: 0
  background: $color-background
  .back
    position: absolute
    top: 0
    left: 6px
    z-index: 50
    .icon-back
      display: block
      padding: 10px
      font-size: $font-size-large-x
      color: $color-theme
  .title
    position: absolute
    top: 0
    left: 10%
    z-index: 40
    width: 80%
    no-wrap()
    text-align: center
    line-height: 40px
    font-size: $font-size-large
    color: $color-text
  .bg-image
    position: relative
    width: 100%
    height: 0
    padding-top: 70%
    transform-origin: top
    background-size: cover
    .play-wrapper
      position: absolute
      bottom: 20px
      z-index: 50
      width: 100%
      .play
        box-sizing: border-box
        width: 135px
        padding: 7px 0
        margin: 0 auto
        text-align: center
        border: 1px solid $color-theme
        color: $color-theme
        border-radius: 100px
        font-size: 0
        .icon-play
          display: inline-block
          vertical-align: middle
          margin-right: 6px
          font-size: $font-size-medium-x
        .text
          display: inline-block
          vertical-align: middle
          font-size: $font-size-small
    .filter
      position: absolute
      top: 0
      left: 0
      width: 100%
      height: 100%
      background: rgba(7, 17, 27, 0.4)
  .bg-layer
    position: relative
    height: 100%
    background: $color-background
  .list
    position: fixed
    top: 0
    bottom: 0
    width: 100%
    background: $color-background
    .song-list-wrapper
      padding: 20px 30px
    .loading-container
      position: absolute
      width: 100%
      top: 50%
      transform: translateY(-50%)
</style>
